In the copending application of Robert B. Morris, Ser. No. 587,600, filed June 6, 1975, and assigned to the assignee of the present application, there is shown and described a brake apparatus that embodies a plurality of brake shoes each of which, during a brake application, is pressed against a corresponding braking surface by a movable member between which and each pair of brake shoes there is interposed a mechanism that includes either a lever pivoted intermediate its ends on the movable member with one of a pair of brake shoes secured to each end of each lever, or a plurality of encased spherical members.
With either of the above-mentioned mechanisms interposed between a pair of brake shoes and the movable member, when the rate of wear of either one of the pair of brake shoes exceeds that of the other, the total force applied to other brake shoe remains the same. However, the force applied to the portion of the brake shoe having the lower rate of wear adjacent one edge thereof is greater than the force applied to that portion of this brake shoe adjacent its other edge. In other words, the braking force is not uniformly distributed over the entire braking surface of the brake shoe so that the braking surface of the brake shoe tends to become tilted with respect to the peripheral surface of the corresponding wheel or brake drum. It is apparent that this tendency of the braking surface of the brake shoe to become tilted with respect to the peripheral surface of the corresponding wheel or brake drum will cause the braking surface of that portion of the brake shoe adjacent one edge thereof and subject to the higher braking force to wear away faster than the remainder of the braking surface of this shoe. Of cource such uneven wear of the braking surface of a brake shoe is undesirable.
Accordingly, it is the general purpose of this invention to provide a novel brake apparatus wherein the mass, and, therefore, the heat sink, of a railway vehicle wheel is increased by securing a brake drum to the side of the wheel, or to the axle on which the wheel is mounted, and applying a braking force from a movable member to the braking surfaces constituted by the peripheries of both the wheel and the drum via a multi-brake shoe means that comprises a plurality of brake shoes. Between each pair of brake shoes and the movable member there is interposed a lever pivoted intermediate its ends on the movable member with its respective opposite ends in sliding abutting contact with shanks that extend from one side of brake heads to the other side of which the brake shoes are secured whereby, upon movement of the movable member in the direction of the wheel and brake drum, these brake shoes, without a tendency to become tilted with respect to the corresponding braking surface, transmit substantially equal braking forces to the peripheral braking surfaces on the wheel and drum notwithstanding the rate of wear of one brake shoe exceeding that of the other.